I looked up and down the street. We were on the edge of Hampstead affluence. Businesses were either booming or going bust. Apart from the galleries, there were a few restaurants and clothes stores, but over half of them had closed down. The buildings all had exactly the same wrought-iron railings as Nereus. The blue and red lights of burglar alarms blinked on even the most modest buildings.

‘Let’s go,’ I said. ‘I’ve got another call to make. Where should I drop you?’

‘I’ll come with you.’

I looked at her. How old was she? Twenty-five? Younger?

‘Don’t you have a life to go to?’ I said.

‘I can’t see my boyfriend tonight.’ A beat. ‘He has to have dinner with his wife.’ Another beat. ‘It’s her birthday.’

She toed the broken beer bottles, then pushed aside an empty pizza box with fossilised cheese on its side.

‘A man lives here,’ she said.

‘How do you know it’s a man?’

‘Only men live like this. Men and pigs.’

Holloway was a few miles and several light years away from Hampstead.

Wren and I stood before a large dusty shop window where pride of place was given to a showroom dummy dressed as a German soldier from World War Two.

‘How’d you know about this place?’ Wren said.

‘I dicked about on Google,’ I said.

Under its coalscuttle helmet the mannequin had the gently pouting features of a young male model. But the clothes he wore were heavy and harsh and made for invading Russia. A thick wool greatcoat was draped over a rough tunic, both far too large for the delicate, snake-hipped dummy, and baggy trousers were tucked into leather boots. It all looked impossibly old and fragile, as if it would disintegrate with one touch.

‘Is any of this stuff real?’ I wondered.

‘Those boots aren’t,’ Wren said. ‘Everything else might be. But the boots – never. The Krauts wore their boots out. On the Eastern Front the Germans used to saw the legs off dead Russian soldiers and defrost them in some lucky peasant’s oven, just to get at the boots.’

I stared at her.

‘My dad,’ she said. ‘He liked World War Two. Is that the expression? Liking it? He was interested, let’s say. The World at War boxed set and all that.’

The rest of the window was full of lovingly presented junk. Buttons. Posters. Faded scraps of metal and cloth and card and leather, all of it displayed like holy relics. SECOND FRONT, it said above the store. COLLECTIBLE MILITARIA.

The lights were going out inside.

I cop-knocked on the door. A long-haired man, not young, stuck his head around the door.

‘I’m just closing up,’ he said.

‘Don’t let us stop you.’

He stood to one side at the sight of our warrant cards and we went in.

‘DC Wolfe and TDC Wren,’ I said.

‘Nick Cage,’ he said, reluctantly.